A. Field of the Invention
The present invention is directed to head gimbal assemblies utilized in hard disk drive assemblies. More specifically, the present invention pertains to a head gimbal assembly comprising suspension design comprising an integrated plurality of trace connections designed to improve, among other things, performance during vibration, shock events, and high-speed rotation.
B. Description of the Related Art
Presently, the hard disk drive industry is observing great success in the consumer electronics environment. One of the main reasons for this success is the ability to achieve ever increasing storage capacity reflecting consumer demand. So far, these advancements are being achieved with minimal cost compared to other competitive technologies.
However, continuing these advances require overcoming arising design and manufacturing difficulties. These difficulties can be found both in the drive level and the component level.
Hard disk drives (HDD) are normally utilized as the major storage units in a computer. Generally, HDDs operate by retrieving and storing digitized information stored on a rotating disk. This retrieving and storing (i.e., “reading” and “writing”) is done by a magnetic “head” embedded on a ceramic “slider” which is mounted on a “suspension”. The assembled structure of slider and suspension is usually called the head gimbal assembly (HGA).
FIG. 1 illustrates a typical slider body embodiment. As shown in FIG. 1, an air bearing surface (ABS) design 102 known for a common slider 100 may be formed with a pair of parallel rails 106 and 108 that extend along the outer edges of the slider surface facing the disk. The two rails 106 and 108 typically run along at least a portion of the slider body length from the trailing edge 110 to the leading edge 112. The leading edge 112 is defined as the edge of the slider that the rotating disk passes before running the length of the slider 100 towards a trailing edge 110. The transducer or magnetic element is typically mounted at some location along the trailing edge 110 of the slider as shown in FIG. 1.
In this embodiment, the rails 106 and 108 form the air bearing surface on which the slider flies, and provide the necessary lift upon contact with the air flow created by the spinning disk. As the disk rotates, the generated wind or air flow runs along underneath, and in between, the slider rails 106 and 108. As the air flow passes beneath the rails 106 and 108, the air pressure between the rails and the disk increases thereby providing positive pressurization and lift.
FIGS. 2a-b illustrates a typical disk drive embodiment. FIG. 2a illustrates spindle motor 102 that spins disk 101. Head gimbal assembly (HGA) 104 controls the head 103 flying above the disk. Typically, voice coil motors (VCM) are used to control the motion of head gimbal assembly 104 over the magnetic hard disk.
In the present art, micro-actuators are now being used to “fine-tune” the head placement because of the inherent tolerances (dynamic play) that exist in positioning a head by a VCM alone. This enables a smaller recordable track width, which in turn increases the density the “tracks per inch” (TPI) value of the hard disk drive. FIG. 2b is an exploded view of the aforementioned elements of FIG. 2a. 
FIG. 3a-c illustrates various views of a typical HGA embodiment. FIG. 3a illustrates a typical HGA embodiment comprising a suspension 213 to load micro-actuator 205 with a head slider 203. Suspension 213 may comprise base plate 215, hinge 216, and load beam 217. Flexure 218 may be attached to hinge 216 and load beam 217 (e.g., through laser welding). Traces 210 may be laminated on the flexure 218, and may comprise two group leads 215a and 216a to electrically couple head slider 203. Traces 210 may also extend outwardly beyond the edges of flexure 218. Spaces 220a and 220b may be located between leads 215a and 216a and flexure 218. Traces 210 may also comprise leads 217a and 217b may extend from the middle region of flexure 218 and extend along both sides of suspension to electrically couple micro-actuator 205. Traces 210 may be electrically connected to suspension bonding pads 206.
FIG. 3b illustrates a typical metal frame micro-actuator structure incorporating a slider. Micro-actuator 205 may comprise metal frame 230 further comprising side arms 211 and 212. Micro-actuator 205 may further comprise bottom support arm 216 and a top support arm 215, which may be coupled to side arms 211 and 212. Top support arm 215 and bottom support arm 216 may be mounted on suspension by epoxy or laser wielding. Slider 203 may be mounted on top support arm 215 (as shown). Two PZT elements 207 and 208 may be attached along the outside of two side arms 211 and 212, and may be electrically connected to leads 217a and 217b (as described above).
FIG. 3c illustrates a metal frame micro-actuator mounted on a suspension. In this embodiment, electric balls 208a electrically couple slider 203 to suspension traces 210 and electrical balls 209 couple PZT element 207 and 208 to suspension traces 210 on each side of the side arms 211 and 212. Electrical connection balls 209 may electrically couple micro-actuator 205 to suspension traces 210. Electrical connection balls may be fabricated by, for example, gold ball bonding or solder ball bonding.
FIG. 4a is an exemplary illustration of the movement of a micro-actuator. When an electrical current is applied through suspension leads 217a and 217b, PZT elements 207 and 208 may expand or contract, causing side arm 211 or 212 to bend in a common lateral direction. For example, in the first half period, the PZT element 207 will shrink and cause the side metal arm 211 to deform and move slider 203 toward the left side. Conversely, when the voltage go to the second half period, the PZT element 208 will shrink and cause the side metal arm 212 to deform and move slider 203 toward the right side. In addition, in the case of the embodiment described in FIGS. 3a-c, spaces 220a and 220b and the flexibility of the two leads 215a/216a allow slider 203 to freely move when directed by micro-actuator 205.
During operational motion, a micro-actuator/slider embodiment typically generates lateral inertial forces (“reaction forces”) that may cause unwanted resonance throughout the HGA. FIG. 4b illustrates a typical micro-actuator/slider embodiment that may experience resonance. In operation, when a sine voltage is input to operate the micro-actuator, in the first half period, one side arm 307a may bend toward out side (indicated by arrow 300a). In doing so, it may also generate a reaction force Fa in the other direction. And since the micro-actuator frame is typically mounted to suspension (e.g., as shown in FIG. 3c), the reaction force Fa may transfer to the suspension and cause unwanted resonance. Similarly, when reversed, the other arm 307b may bend to the other side to generate a reaction force Fb, causing unwanted resonance as well. This resonance may affect the dynamic performance of the HGA and limit the servo bandwidth improvement of the hard disk drive.
Design improvements in performance of hard disk drives are often accompanied by increases in spindle RPM (rotation per minutes). In such cases, the motion of the rapidly rotating disk may create a turbulent flow of air (“windage”) that may affect the performance of the hard drive components. In the case of the HGA embodiments with traces with spaces to ensure free movement (see e.g., FIG. 3c), the generation of a turbulent airflow may bear on nearby traces continuously during motion, and may, in some circumstances, even cause trace displacement.
FIG. 5 illustrates effects of trace turbulence as observed in typical HGA embodiments. As illustrated in FIG. 5, the turbulent flow of air may cause trace 215a to sway toward the backside of the load beam, while trace 216a may sway toward the top side of head slider 203. In other instances, traces 215a and 216a may sway toward the same side. These displacements may disrupt the proper movement of the head, thereby affecting the static and dynamic performance of the head and the performance of the hard disk drive as a whole.
Therefore, there is a need for a head gimbal assembly with improved characteristics that address at least the aforementioned problems.